JPS60183511A - Angle sensor - Google Patents

Abstract

PURPOSE:To reduce the size of the angle sensor and to improve its sensitivity by deflecting a light beam passed through a pinhole perpendicularly by a reflection mirror through a half-mirror and making it incident on the surface of mercury liquid, and providing a semiconductor position detecting element on the image forming surface of an image forming lens which converges its reflected luminous flux. CONSTITUTION:Parallel light from a light source 1 and condenser lens 2 is made incident on the (x)-axial reflecting surface 6 of a prism 5 through the half-mirror 4, its reflected light is made incident on the liquid surface 7 in a mercury tank 12 on a horizontal table 11 whose horizontal surface is adjustable, and further its reflected light is converged on a semiconductor position detecting element 14 on the image forming surface of an image forming lens 13 through the surface 6 and mirror 4. Similarly, the reflected light of the reflected light from the (y)- axial reflection mirror 8 through the surface 7 is converged on the element 14, whose output is led to an electronic circuit (not shown in a figure) to calculate and display the (x) and (y) component of the tilt angle theta of the surface 7 on a display device (not shown in the figure) simultaneously.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an angle sensor used in electronic goniometers and the like.

Many devices have been proposed and put into practical use as angle sensors. For example, there are mechanical or electromagnetic angle sensors that use the movement of a weight hanging from a rotating shaft and read the rotation angle with an encoder, or convert it into the amount of excitation current of an electromagnetic rotor. . However, all of these methods involve friction in the rotating bearing and many coupling error factors with sensors such as encoders, and can only detect the inclination angle of only one of the χ and y axes. In order to carry out simultaneous measurement of Ic, it is necessary to install two of these angle sensors, which inevitably leads to drawbacks such as an increase in the size of the device and a corresponding increase in cost. Therefore, in recent years, the mercury liquid level has been used as a horizontal reference, and by using this as an optical mirror surface to project concentric ring patterns etc. onto the mercury liquid surface, the deflection of the diffraction image generated by the original pattern of the reflected image has been improved. A so-called optical angle sensor that photoelectrically detects the angle has been proposed.

Using the optical image in this way, the tilt angle χ, y2 $11
Although it has many advantages over mechanical and electromagnetic angle sensors such as dual sets because it can automatically measure one component without contact, conventional optical angle sensors have It was large and had problems in terms of sensitivity.

The present invention has been made in view of two points, and it eliminates the drawbacks of mechanical or electromagnetic angle sensors and automatically measures the angular components of the tilt angle in the χ and y directions simultaneously and without contact. It is an object of the present invention to provide a highly sensitive angle sensor which is relatively inexpensive and has a mechanism similar to that of Combat 1.

Hereinafter, the present invention will be described in detail based on the drawings.

FIG. 1 is a schematic diagram of an angle sensor according to an embodiment of the present invention. In FIG. 1, the orthogonal coordinates χ+ytZ
Define the system and set the vertical direction as the Z axis. Measurement of inclination angle is χ, y
The explanation will be made for two axes at the same time, but since the illumination system for the light beam and the light receiving system i have exactly the same configuration for both axes, only the χ axis will be described.

A small, directional, quasi-monochromatic light source such as an LED 1
The luminous flux from the condenser lens 2 becomes parallel light and passes through the pinhole 3. The diameter of the pinhole 3 is selected to a value that does not cause diffraction, for example, about 1 manφ. The parallel light beam transmitted through the pinhole 3 is reflected by the semi-transparent mirror 4 installed at an angle of 45 degrees with respect to the optical axis, enters the reflective surface 6 of the prism 5, and is irradiated vertically downward onto the mercury liquid surface 7. . The prism 5 has a reflecting surface 6 having a χ-axis angle and a reflecting surface 8 having a y-axis circumference. It is configured to deflect each ray of light vertically downward by exactly 90° (
The intersection angle between both reflective surfaces 6 and 8 is 120°).

In FIG. 1, the prism 5 is shown larger than other optical members, but in reality, it only needs to reflect a light beam of about 1 mmφ, and the installation location is close to above the mercury liquid level 7. , extremely minute dimensions.

Any shape is fine. In addition, as described later, the optical path length is also 50
Since the length is as short as m + n, all other optical members are also so-called micro optical members.

Therefore, the incident spot positions 9 and 10 on the mercury liquid level 7 for the χ-axis pressure, y 11+, are very close to each other at the center of the liquid level 7.

Mercury 4175 is used for the horizontal table 11 that can finely adjust the horizontal surface.
12 is fixed, forming a liquid surface 7 that is a horizontal plane reference and a good reflective surface. The light beam reflected on the liquid surface 7 is reflected again on the reflective surface 6 of the prism 5, passes through the semi-transparent mirror 4, and then enters the imaging lens 13, which is provided on the imaging surface of the imaging lens 13. The light is focused on a semiconductor device detection element (hereinafter referred to as PSD) 14''.

If the light beam incident on the liquid surface 7 is vertical, the focal point on the PSD 14 is its center point P. However, the incident light flux is O from the vertical line.
If the lens is tilted by 1, the focal point will be deviated from the point Po and become the point P.

The PSD 14 has electrodes PI+P2, and the output 15 of the PSDI/I has distances P, P from the electrode P to the focal point Pχ.
A photocurrent proportional to the current is induced.

PS used as PSD 1'4 in this example
D is already commercially available.For example, Hamamatsu Photox Co., Ltd.
A one-dimensional PSD, such as 314.53, can be used. This type of PSD has a positional resolution of 0.2 μm and a response speed of 5 μsec, making it possible to detect the light spot position extremely quickly and with high precision.

Now, if the optical path length from the incident point 9 to the center point Po of the PSD 14 is Q, and the angle of inclination from the horizontal plane is 0, then Po P,, = 2QO, and in order to read this angle of inclination O with a resolution of, for example, 5'', Determine the required optical path length Q. Set the resolution of PSD14 to 0.
If it is 2 μm, then Q is 4.2 mm, which means that a 5″ angle can be measured with an extremely short optical path length.

However, in reality, the optical path length is 5 due to constraints on the arrangement of optical components.
It is preferable to select it to be about 0 mm. Further, since the light receiving surface shape of the PSD illustrated here is I x 3 mm, when the optical path length is Q-50 mm, the measurable inclination angle range with respect to the short side of 1 mm is ±17'. What should be noted here is that the slope of the liquid level 7 is in any direction on the χy plane, so the direction of movement of the condensing point P is the direction of the electrode P 1 +1]2 of PSD 14.
It is a point that is aligned with the axis 16 that connects the .

In the rectangular light-receiving surface configuration as described above, the lateral angle measurement range becomes extremely narrow. In order to expand the angle measurement range, it is possible to use a PSD with a square light-receiving surface, such as Hamamatsu Ho1-X S], 662 (light-receiving area 13 x 13 mm), but its positional resolution is slightly lowered to 6 μm.

FIG. 2 is a schematic diagram of another embodiment of the angle sensor according to the present invention. Incidentally, the same members as those shown in the first figure are given the same reference numerals, and the description thereof will be omitted.

This embodiment differs from the embodiment shown in the first drawing in that the prism 5
A reflecting mirror 17 is provided instead of , and -dimensional P S D 1
．． 4 is replaced by a two-dimensional PSD 18, and the irradiation and reflection paths of the light beam are the same as those described above.

The two-dimensional PSD 18 has a pair of χ-axis circumferential electrodes P, P2 and a y-axis angular electrode P3 on opposite sides of a square as shown in the third diagram.
P4 is provided, and a pair of photocurrent outputs proportional to the χ and y coordinates of the focal point P can be obtained.

This PSD 18 has a two-layer structure in which the current dividing resistance layer, which is a light-receiving layer, has a two-layer structure.

There is a commercially available device that does not cause interference between y-position signals and has a resolution of 6 μm and a position detection error of ±1.5%.

This embodiment can be configured with only one light source and one PSD,
The surface also has the advantage of being able to automatically measure the position of the monkey light spot on the χ and y axes at the same time.

FIG. 4 is a block diagram showing an embodiment of an electronic circuit system that processes position signals from the PSD. Electronic circuits 20 and 2
1 is for the χ-axis circumference and the y-axis, respectively.

Since the signal processing method is the same, only the electronic circuit 20 will be described.

A set of photocurrents generated by the focal point PL are respectively input to current-voltage converters 22,23.

Now T5 earring j, '=Q, , P21) 工=Q2.
If the proportionality constant is r, the output of the current-voltage converter 22 is rQ1
+The output of the current-voltage converter 23 is rQ2. These two outputs are sent to the next stage adder 24. It is input to the subtracter 25 and gives respective outputs r (Q1+Q2) and r (Qla2). The outputs of the adder 24 and the subtracter 25 are sent to the next stage, the divider 2.
The output voltage V=(Q+Q,)/(Q++Qz) is divided by G, and the χ-axis component of the inclination O is Output.

Further, the electronic circuit 21 outputs the y component of the tilt angle O, and the display 27 simultaneously displays the χ component and ) component of the tilt angle O processed by the electronic circuits 20 and 21, respectively.

As described above, the angle sensor according to the present invention uses the mercury liquid level as a reference horizontal plane and as a good reflecting surface, and makes the polarization of the reflected light spot by this surface in the orthogonal two axes directions at a high speed of PSD. By using a photoelectric conversion function with high resolution, it becomes possible to perform automatic shoulder-side adjustment at the same time. In addition, since it is relatively inexpensive and has a simple configuration, it is highly effective in practical use.

Incidentally, the present invention exemplifies inclination angle measurement from a vertical line with a compensator in electronic angle measurement H:÷, etc. in mind. However, the reflective surface does not necessarily have to be a horizontal surface;
It may also be a reflective surface of a oriented metal or glass mirror. Therefore, the angle sensor according to the present invention can be expected to have a wide range of applications as a precise automatic angle measuring instrument or angle measuring sensor in the field of so-called Δ1 control equipment.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of one embodiment of the present invention, Fig. 2 is a schematic diagram of another embodiment of the invention, and Fig. 3 is a front view of the two-dimensional 1) S I) used in the embodiment shown in Fig. 2. Figure 4 is l) S
FIG. 2 is a block diagram illustrating an embodiment of an electronic circuit system for processing a positional symbol from D. FIG. 1 Light source 2 ・Condenser lens 3... Pinhole 4 ・Semi-transparent mirror 6.8 Reflecting surface (reflector) 7 ・Mercury liquid level 11... Horizontal table 12 ・Mercury tank 13... Imaging lens 14... - dimension Semiconductor device detection element 17...reflector] 8...Two-dimensional semiconductor device detection element 20.2]...Electronic circuit 27/display Patent applicant Asahi Optical Co., Ltd. Kinuta 1 Zuka 2□□□

Claims (1)

[Claims] a light source, a condenser lens that converts the light beam from the light source into parallel light, a pinhole that allows a portion of the parallel light from the condenser lens to pass through, and a semi-transparent mirror that reflects a portion of the light that has passed through the pinhole. 1. An illumination system comprising a reflecting mirror that deflects the light reflected by the semi-transparent mirror vertically downward; 1. A mercury tank arranged on the optical path from the illumination system and fixed to a horizontal table; 1. a light receiving system comprising an imaging lens that directs the reflected light beam from the mercury liquid surface; and a semiconductor device detection element provided on the imaging surface of the imaging lens; processing signals from the semiconductor device detection element; An angle sensor consisting of an electronic circuit system and a display that independently displays tilt angle components in two orthogonal horizontal axes directions, which are outputs of the electronic circuit system.